Attachment plug



Sept. 23; 1-924, 1,509,672

A. c. GAYNQR ATTACHMENT PLUG Filed March 4, 1922 ltd Patented Sept. 23, 1924.

UNITED STATES ARTHUR C. GAYNOR, 0F STRATFORD, CONNECTICUT.

ATTACHMENT PLUG.

Application filed Karen 4, 1922. Serial No. 541,031.

To all whom it may concern:

Be it known that I, ARTHUR C. GAYNOR, a citizen of the United States, and a resident of Stratford, county of Fairfield, State of tonnecticut, have invented certain new and useful Improvements in Attachment Plugs, of which the following is a specification.

This invention relates to an attachment plug and moreparticularly to a base for a separable attachment plug for electric wirin systems.

llugs of this type are commonly formed of a block of insulating material having cavities adapted to receive the blades of a separable cap member and provided with contact plates in the cavities through which connection is made to a socket in which the plug may-be inserted. For this purpose the plate of one of the cavities is connected to a threaded metallic shell surrounding a portion of the insulating block on which it is rigidly mounted and adapted to fit into and make contact with the walls of the socket. The contact plate of the other cavity is connected to a metallic button mounted on the end of the plug and adapted to contact with a plate at the bottom of the socket.

In these plugs the requisite tightness between the contacts of the socket and those of the plug is obtained and the plug is retained in osition, by screwing the plug tightly against the bottom of the socket and thereby creating a longitudinal or sidewise pressure against the sides of the threads of the socket and against the end of the plug. There is consequently a tendency for the plug to work loose from the socket, particularly when subjected to vibration, and to permit an arc to form between the contacts of the plug and socket as they separate, thereby causing danger of fire through overheating. The necessity for screwing the plug tightly into the socket also causes a strain between the contact shell of the plug and the body of the plug which tends to break or loosen the solder or rivets by which the shell is fastened onto the plug body and in this manner break, the electric connection and give rise to an additional danger of overheating. Plugs of this type also require the use or indirect connections between the contact plates which connect with the cap blades and the socket connections,necessitating the use of solder for joining the connections and creating points of weakness when the plug is used under conditions. in which the solder may become melted. When the plug is being inserted into or removed from the socket and a portion of the shell is in contact with the wall of the socket and a portion is exposed there is also a danger of the user touching the exposed end of the shell and receiving a shock or of a pull chain of another lighting fixture or appliance touching the exposed shell.

An object of the present invention is to provide a plug which is simple and inexpensive in construction and which is safe in operation.

Another object of the invention is to provide a plug which provides little opportunity for contact with electrically charged parts of a socket as the plug is inserted into or removed from the socket.

Another object of the invention is to provide a wall or inner plug for separable attachment plugs having a conductor consisting of a single element, which element atfords the electrical connection between the contact blade and the socket into which the wall plug is inserted.

A still further object ot' the invention is to provide a plug which avoids the use of a threaded metallic shell and provides a threaded portion of insulating material and a gripping or locking means or portion to hold the plug in the socket without the necessity of tightly screwing the plug into the socket.

In the separable attachment plugs constructed heretofore, a single contact plate has usually been provided in each attachment cavity so arranged that it would lie parallel or fiat on'the cap blade when a blade of the proper thickness was used but which would not lie flat on the blade and would provide only aslight contact surface when a slightly thicker or thinner blade was used.

Accordingly another object of this invention is to provide a plug in which the contact blades will form a maximum contact for diderent thicknesses of blades. @ther features and objects of, the invention are to avoid the use of soldered connections in the plug, to make the threaded portion of the plug on non-conducting material in conjunction with either a threaded or unth'readed member to engage the socket and to rovide a plug which may be easily assemb ed and will stay permanently assembled.

-With these and other objects in view, the

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plates or leaves are so formed invention comprises the device described and set forth in the following specification and claims:

The various features of the invention are illustrated in the accompanying drawings, in which:

Fig.- 1 is a front elevation of a separable attachment plug forming a preferred embodiment of the invention.

Fig. 2 is a sect-ion of the plug taken on line 22 of Fig. 1, showing the contactplates and electrical connections in the plug.

. Fig. 3 is a sectional view on a plane similar to thatcf Fig. 2 but showing certain parts in a position which they occupy while being inserted in the construction of the p Fig. 4 is a perspective view of one of the1 contact plates removed from the plug, an

Fig. 5 is a perspective view of another contact member adapted to co-operate with the member shown in Fig. 4.

In the present invention, the use of a threaded shell is avoided and the body of the plug, including the threaded portion which fits into the socket is formed entirely of insulating material. Connection with.

tudinally through the'p ug ofi insulating material suitably spaced to receive the blades of the separable cap member. In one of these passages or cavities resilient plates or leaves are positionedl'which extend through the lower or inner end of the passage and are bent to form the end contact. One of the contact plates or leaves of the other cavity has an ofiset portion adapted to extend outwardly through a side opening to the threaded part of the plug and a face portion adapted'to form a fiat contact with a'blade inserted into the cavity. The other contact plate or leaf has a spring portion adapted to press the outwardly offset portion of the other member and a face portion adapted to form a flat contactwith the blade inserted into the cavity Tljpse t y may be separately inserted into th cavity, and when lock together so that they can not be readily removed. N0 portion of these blades or leaves isiexposed except the small portion in the threaded portion of a block of insulating material 10 having a portion 1(2 threaded to fit the threads of a socket into which the plug may be inserted and a portion 14 adapted to project from the socket a short distance. Two cavities or passageways 16 and 18 extend longitudinall through the plug and have narrow mout s or openings 20 and 22 at the outer end of the plug through which the blades 24 of a separable cap 26 are adapted to be inserted. The passage 16 is also provided with a side opening or passage 28 o ening through the threaded surface 12 o the plug. The body of insulating material may be formed in an desired manner but is preferably formed 0 a single piece of molded material in which the assages may be formed as the materia is molded or may be subsequently formed in the molded block.

Two contact plates or leaves 30 and 32 are inserted or positioned in the passage 16 in such a manner that they may form an effective contact with the blade 24 of the separable cap as the latter is inserted into the plug and to form a resilient contact with the threaded wall of the socket into which the plug is inserted. To this end the member 30 is shaped to provide a substantially flat portion 34 adapted to be held resiliently in a longitudinal position in the passage 16 by means of an outwardly bentend 36 and a step or shoulder portion 38 which are. adapted to rest against the .outer wall of the passage. The member 3 Q.is also provided with an end portion 40 adapted to rest against the outer. .wall of the passage and an intermediate portion 41 bent or offset to project outwardly through the side opening 28 of the passage 16 and havin a threaded face 42 ads ted to lie slight y outside thesurface of t e plug as the shoulder 38 and the end portion 40 lie in contact with the wall of the passage 16. In the form of the invention illustrated in the accompanying drawing the projecting face of the member is grooved to corre- S 0nd to and to lie in ali ment with the t reads of the plug but t is is not essential although it is a preferred construction. The face 42 provides a contact with the side wall of the socket and also acts as a retaining member to resist the loosening of th plug without the necessity for crea ing a side or longitudinal thrust on the plug. v

The other contact leaf member 32 is also provided with a substantially fiat contact face 44, adapted to contact with the adjacent sflide or face of the blade inserted into the cavity 16, and a bent end 46 and an offset face 48 positioned to lie a inst the side wall of the cavity and maintain the face 44 in its proper position. Extending diagonally upward from the lower end of the face 48 is a spring or resilient portion 50 of the member 32 from the upper end of which a flat bearing plate portion 52 extends downwardly in a position substantially parallel to the portion 48. The hearing plate 52 bears against the member and presses the face 42 toward its outermost position but permits the face 42 to be pressed inwardly against the action of the spring as the plug is screwed into a socket. a

The member 30 is of such a shape that it may be inserted singly through the large or lower end of the cavity or passage 16 and falls readily into position with the face portion 42 extending into the side passage 28. The member 32 may then be inserted and holds the member 30 in its proper position. The end of the member 30 is provided with a projecting pin or lug 54 adapted to enter a corresponding opening 56 in the plate 52 when the members are in their proper position relative to each other. When the members 30 and 32 are inserted into the cavity as described above the pin 54 locks and holds the members in position so that they can not be readily dislodged or removed and the members form a permanent, direct and homogeneous connection from the socket to the blade of the separable cap.

The cavity or passage 18 is provided with contact blades 58 and 60 which extend out of the lower end of the cavity and have bent portions 62 and 63 which are fastened to the end of the plug by means of a rivet 64 molded in the end of the block 10. The bentportion 63 is adapted to contact with a terminal plate in the bottom of the socket and upon the insertion of the blades 24 the blades 58 and 60 have flat, substantially parallel contact portions in engagement with the blade 24 and resiliently supported by outwardly curved ends 66 andv 67 and olfsets or projections 68 and 69 resting against the o posite walls of the passage 18. As the blade 22 of the separable cap 26 is inserted into the outer end of the cavity 18 it forms a long parallel contact with the adjacent faces of the blades 58 and 60, the offset portions and turned ends of the plates causing the faces to remain in a substantially parallel position when blades of different thickness are inserted.v The use of double blades also tends to insure that at least one of the contact faces lies flat against the blade. The construction of the plates 30 and 32 is also such as to provide a long surface of contact with the blade inserted into the cavity.

The particular form of the invention described above is particularly adapted and suitable for separable cap plug but it may be adapted for a number of other types of plugs as, for example, a plug fuse.

It is to be understood that other means for securing or fitting the plug into a socket thai the screwthreaded connection may be use Through the above described invention a plug body having a minimum of parts and of metal is required and the plug body is made of a single piece of molded insulating material thus eliminating scrap and waste in the manufacture of the device. The small amount of metal conductor parts exposed as the plug is inserted into a socket reduces the danger of a shockbeing received by contact with these parts to substantial safety. The absence of soldered parts, the provision of single, homogeneous conductor and the removal of the necessity of putting the plug under a strain to insure its retention in the socket. plug is also such that it resists rough treatment which would dent or separate the parts of an ordinar plug.

Having describe the invention what I claim and desire to secure by Letters Patent is: l

1. A device of the kind described which comprises a body of insulating material having a screwthreaded portion adapted to fit a socket, cavities extending through said body of insulating material, one of said cavities having a side passage to said threaded portion and separable spring members in said passage adapted to resiliently engage a blade member inserted into said passage and one of said members having a face resiliently mounted in said side passage and forming an outwardly pressed member adapted to engage the side of the socket and hold the body of insulating material in position.

2. A device of the kind described which comprises a body of insulating material hay,- ing a portion adapted to'be inserted into a socket, conductor members in said body of insulating material adapted to frictionally engage the blades of a detachable cap attachment, one of said conductor members extending through theend of said body of insulating material and adapted to contact with the bottom of the socket and the other conductor member having a resilient member normally extending slightly outside the surface of said body of insulating material to resiliently bear against the side wall of a socket.

3. A device of the kind described which comprises a body of insulating material adapted to be inserted into a socket and 'having a cavity opening at an end of the body of material and at the side of the portion insertable into the socket, a conducting member adapted to lie in said cavity and having a portion projecting to the edge of said side opening and a member adapted to be inserted in said cavity and to resiliently press said projecting portion of said conductor member outwardly in said side opening, said 1 The construction of the l conductor being adapted to resiliently engage a blade inserted into said cavity.

4. A device of the kind described which comprises a body of insulating material adapted to be inserted into a socket and having a cavity opening at an end of said body of material and opening to the side of said portion insertable into said socket, a conducting member adapted to lie in said cavity and having a portion projecting to the edge of saidside opening, a member adapted to be inserted into said cavity and to resiliently press said projecting portion of said conductor member outwardly in said side opening and means on said members for locking said members in position in said cavity, said member being adapted to resiliently engage a contact blade inserted into said cavity.

5. In a device of the kind described, a body of insulating material having a cavity opening through an end of said body and a side extension of said cavity, a member in said cavity having an offset portion extending into the side extension of said cavity and a resilient member pressing said offset portion into said side extension and locking with said member to prevent removal of said members, said ofi-set and resilient members being adapted to engage a contact blade inserted into said cavity.

6. A device of the kind described which comprises a body of insulating material adapted to be inserted into a socket and having a cavity opening at the ends of said body andlopening sidewise through the side wall of said body, a metallic contact member having an offset portion projecting through said sidewise opening and having a contact portion held resiliently and slightly spaced vfrom one wall of the cavity, and another coning a longitudinal cavity opening at the ends of the body and sidewise through a side wall of the body, and a pair of contact members resting against opposite walls of said cavity, one of said members having a portion projecting through said sidewise opening and r the other member having a spring portion pressing said projecting portion into said opening.

8. A device of the type described which comprises, a body of insulating material adapted to be inserted into a socket and having a longitudinal cavity into which a contact blade may be inserted, and a pair of contact members in said cavity resting against opposite walls of said cavity at two spaced points and having intermediate portions resiliently pressed towards each other and being parallel when the contact blade is in circuit making position.

In witness whereof I have hereunto set my hand at Bridgeport, county of Fairfield, State of Conn, this 27 day of February,

ARTHUR C. GAYNOR. 

